diff --git a/pkg/kubelet/config/config.go b/pkg/kubelet/config/config.go
index 99a08b69d3c..de895cc98d7 100644
--- a/pkg/kubelet/config/config.go
+++ b/pkg/kubelet/config/config.go
@@ -90,14 +90,14 @@ func (c *PodConfig) Channel(source string) chan<- interface{} {
 	return c.mux.Channel(source)
 }
 
-// SeenAllSources returns true if this config has received a SET
-// message from all configured sources, false otherwise.
-func (c *PodConfig) SeenAllSources() bool {
+// SeenAllSources returns true if seenSources contains all sources in the
+// config, and also this config has received a SET message from each source.
+func (c *PodConfig) SeenAllSources(seenSources sets.String) bool {
 	if c.pods == nil {
 		return false
 	}
-	glog.V(6).Infof("Looking for %v, have seen %v", c.sources.List(), c.pods.sourcesSeen)
-	return c.pods.seenSources(c.sources.List()...)
+	glog.V(6).Infof("Looking for %v, have seen %v", c.sources.List(), seenSources)
+	return seenSources.HasAll(c.sources.List()...) && c.pods.seenSources(c.sources.List()...)
 }
 
 // Updates returns a channel of updates to the configuration, properly denormalized.
diff --git a/pkg/kubelet/kubelet.go b/pkg/kubelet/kubelet.go
index e6db9884d49..249a531a7a0 100644
--- a/pkg/kubelet/kubelet.go
+++ b/pkg/kubelet/kubelet.go
@@ -118,7 +118,7 @@ type SyncHandler interface {
 	HandlePodCleanups() error
 }
 
-type SourcesReadyFn func() bool
+type SourcesReadyFn func(sourcesSeen sets.String) bool
 
 // Wait for the container runtime to be up with a timeout.
 func waitUntilRuntimeIsUp(cr kubecontainer.Runtime, timeout time.Duration) error {
@@ -418,6 +418,7 @@ func NewMainKubelet(
 	klet.backOff = util.NewBackOff(resyncInterval, maxContainerBackOff)
 	klet.podKillingCh = make(chan *kubecontainer.Pod, podKillingChannelCapacity)
 
+	klet.sourcesSeen = sets.NewString()
 	return klet, nil
 }
 
@@ -441,6 +442,9 @@ type Kubelet struct {
 	podWorkers     PodWorkers
 	resyncInterval time.Duration
 	sourcesReady   SourcesReadyFn
+	// sourcesSeen records the sources seen by kubelet. This set is not thread
+	// safe and should only be access by the main kubelet syncloop goroutine.
+	sourcesSeen sets.String
 
 	podManager podManager
 
@@ -597,6 +601,15 @@ type Kubelet struct {
 	daemonEndpoints *api.NodeDaemonEndpoints
 }
 
+func (kl *Kubelet) allSourcesReady() bool {
+	// Make a copy of the sourcesSeen list because it's not thread-safe.
+	return kl.sourcesReady(sets.NewString(kl.sourcesSeen.List()...))
+}
+
+func (kl *Kubelet) addSource(source string) {
+	kl.sourcesSeen.Insert(source)
+}
+
 // getRootDir returns the full path to the directory under which kubelet can
 // store data.  These functions are useful to pass interfaces to other modules
 // that may need to know where to write data without getting a whole kubelet
@@ -1618,7 +1631,7 @@ func (kl *Kubelet) removeOrphanedPodStatuses(pods []*api.Pod, mirrorPods []*api.
 }
 
 func (kl *Kubelet) deletePod(uid types.UID) error {
-	if !kl.sourcesReady() {
+	if !kl.allSourcesReady() {
 		// If the sources aren't ready, skip deletion, as we may accidentally delete pods
 		// for sources that haven't reported yet.
 		return fmt.Errorf("skipping delete because sources aren't ready yet")
@@ -1906,7 +1919,7 @@ func (kl *Kubelet) syncLoop(updates <-chan PodUpdate, handler SyncHandler) {
 		// housekeepingMinimumPeriod.
 		// TODO (#13418): Investigate whether we can/should spawn a dedicated
 		// goroutine for housekeeping
-		if !kl.sourcesReady() {
+		if !kl.allSourcesReady() {
 			// If the sources aren't ready, skip housekeeping, as we may
 			// accidentally delete pods from unready sources.
 			glog.V(4).Infof("Skipping cleanup, sources aren't ready yet.")
@@ -1930,6 +1943,7 @@ func (kl *Kubelet) syncLoopIteration(updates <-chan PodUpdate, handler SyncHandl
 			glog.Errorf("Update channel is closed. Exiting the sync loop.")
 			return false
 		}
+		kl.addSource(u.Source)
 		switch u.Op {
 		case ADD:
 			glog.V(2).Infof("SyncLoop (ADD): %q", kubeletUtil.FormatPodNames(u.Pods))
diff --git a/pkg/kubelet/kubelet_test.go b/pkg/kubelet/kubelet_test.go
index 152b97c84eb..e554cb95c6b 100644
--- a/pkg/kubelet/kubelet_test.go
+++ b/pkg/kubelet/kubelet_test.go
@@ -51,6 +51,7 @@ import (
 	"k8s.io/kubernetes/pkg/types"
 	"k8s.io/kubernetes/pkg/util"
 	"k8s.io/kubernetes/pkg/util/bandwidth"
+	"k8s.io/kubernetes/pkg/util/sets"
 	"k8s.io/kubernetes/pkg/version"
 	"k8s.io/kubernetes/pkg/volume"
 	_ "k8s.io/kubernetes/pkg/volume/host_path"
@@ -102,7 +103,7 @@ func newTestKubelet(t *testing.T) *TestKubelet {
 	if err := os.MkdirAll(kubelet.rootDirectory, 0750); err != nil {
 		t.Fatalf("can't mkdir(%q): %v", kubelet.rootDirectory, err)
 	}
-	kubelet.sourcesReady = func() bool { return true }
+	kubelet.sourcesReady = func(_ sets.String) bool { return true }
 	kubelet.masterServiceNamespace = api.NamespaceDefault
 	kubelet.serviceLister = testServiceLister{}
 	kubelet.nodeLister = testNodeLister{}
@@ -393,7 +394,7 @@ func TestSyncPodsDeletesWhenSourcesAreReady(t *testing.T) {
 	testKubelet.fakeCadvisor.On("DockerImagesFsInfo").Return(cadvisorApiv2.FsInfo{}, nil)
 	testKubelet.fakeCadvisor.On("RootFsInfo").Return(cadvisorApiv2.FsInfo{}, nil)
 	kubelet := testKubelet.kubelet
-	kubelet.sourcesReady = func() bool { return ready }
+	kubelet.sourcesReady = func(_ sets.String) bool { return ready }
 
 	fakeRuntime.PodList = []*kubecontainer.Pod{
 		{